This invention relates to motor control systems and methods.
The invention is more particularly concerned with control systems for three-phase motors.
In some applications it is important that motors rapidly reach their operating speed, such as, for example, with motors driving hydrodynamic gas-lubricated bearings which are only subjected to wear before the gas film is fully established between the bearing surfaces. For this reason, it has been the practice to supply such motors at high power to ensure rapid start up. This, however, leads to high power consumption and high operating temperatures which can adversely affect the motor or the system in which it is included.
Another difficulty met in three-phase motor systems is that of determining whether or not the motor is running in synchronism with the power supply.